Embedded Files
Supercritical fluid is a substance at temperature and pressure above its critical point.
The property of supercritical fluid is in between gas and pure liquid so that they are also known as dense gases or compressible liquid.
It can diffuse through solids like a gas and dissolve materials like a liquid A critical point is a particular temperature and pressure at which two phases (like liquid and vapour) can co-exist.
Supercritical fluid has good solvation power, low viscosity, higher diffusibility and good penetrating power.
By the help of super critical fluid extraction technique we can separate the constituents from the drug with the help of super critical fluid.
Generally we can separate the constituents from the solid matrix but it may also be liquid.
CO2 is one of the most common super critical fluid.
To make CO2 super critical fluid the critical temperature is 31°C and critical pressure is 74 bars.
Instrumentation:
The different component in the super critical fluid extraction is the first one is fluid reservoir which contains the fluid like gas cylinder in the case of CO2.
Another one is the pump; the pump may be syringe pump or reciprocating pump.
Another important is the extractor which may be made of stainless steel and can with stand to high pressure like 300 to 600 atmosphere.
Another important component of the super critical fluid extractor is the restrictor.
It is important for the controlled and systematic release of the pressure inside the extractor vesicle.
The restrictor may be a fixed type or variable type.
The isolated constituent is collected in a collector where it can be detected with the help of detector.
Sometimes modifiers are also added into the supercritical fluid to increase its versatility like one to ten percent of methanol is added in CO2.
During the process the liquid is pumped into a heating zone and heated to supercritical temperature then the super critical fluid passes through the extraction vessel where it diffuses to the solid matrix and dissolves the active constituents.
The extracted material with supercritical fluid comes into the separator or collector unit where the pressure is low.
The extracted material settle down here and the CO2 can then be cooled, recycled or discharge to the environment.
The isolated constituent can be detected with the help of detector.
Advantages
1) SFE determines the rate at which the extraction can be performed.
2) The SFE process completes within 20-60 minutes.
3) Many steps have been eliminated from SFE, thus the accuracy and reproducibility of the extraction is increased.
4) SFE produces less waste solvents and also offers less exposure of laboratory personnel to toxic solvents.
5) SFE yields quantitative recovery of target analytes without loss or degradation during extraction.
6) SFE offers selective extraction by selecting the fluid polarity and density.
7) SFE avoids purification by adsorption chromatography and keeps the other active ingredients intact in the matrix.
8) Supercritical fluids have solute diffusivities in order of magnitude higher and solute viscosities in order of magnitude lower than liquid solvents, and this increases the extraction efficiency.
9) The solvent strength of a supercritical fluid can be easily controlled, while the solvent strength of a liquid is constant.
10) The supercritical fluids are mostly gasses at ambient conditions.
Disadvantages
1) Carbon dioxide (the most commonly used solvent in SFE) cannot be used for extracting polar compounds due to its low polarity
2) Presence of water in SFE process may cause problems.
3) In SFE, the matrix effect is unpredictable.
4) SFE process requires specialised/expensive equipment.
Page updated
Google Sites
Report abuse